Bamboo GT disappointing 16km range (street 97mm)

I have emailed evolve again this morning about my motor and battery issues, and I outlined to them how information like this needs to be given when they state stuff like "rider weight i 85kg" on their website as the temperature arguably plays a much bigger role in the battery range than any of the other variants.

 

You guys ride in Eco? I can only tolerate GT. I use Eco when I'm riding with people on bikes.

 

I have had my GTX Since January and have been riding 10ks to work and 10ks home most days, a couple of times I have gone to the gym on the way home and done around 28ks on one charge.
With my bag I probably way around 100KG, and I generally ride at around 30+kmh for most of the trip.
There is a big hill near my house which pushes the battery pretty hard both ways.
Previously the battery would struggle a bit with the hill on the way home and it would sometimes drop back to eco if I tried to keep it at 25kmh up the hill, but I was getting home with the board still running well and displaying the battery in green while skating along the straights.
It is now around 0 in the mornings and 10-15 in the afternoons and my battery is totally struggling. I am having to ride slower in the mornings to conserve battery, and even doing that it quickly drops to yellow on the way home. I have to nurse it up the more gentle hills and slow to a crawl up the big hill.
I am going to try to do a run on a warm weekend day to confirm that it is not the battery playing up, however it feels to me like the cold really screws with the batteries. I have gone from getting around 30ks pushing it pretty hard to having to nurse it through 20ks in the cold weather.